Fireproof thermal insulator



Oct. 29, 1935.

L. D. MORTON 2,018,800

FIREPROOF THERMAL INSULATOR Filed Aug. 29, 1931 Fig.3 2

law/elves Mar/an 1.\'I"ENTOR.

Patented Oct. 29, 1935 'IPIATENT- "OFF-ICE 2,018,800 FI REPROOF THERMALINSULATOR Lawrence D. Morton, Sandusky, Ohio, assignor to The Hinde 8;Dauch Paper 00., Sandusky, Ohio Application August 29, 1031, Serial No.560,119

12 Claims. (01154- 5) The invention to be hereinafter described relatesto fire proof thermal insulators, and more particularly to what is knownas the semi-rigid type of such insulators.

Any medium serving to prevent or retard the passage of heat may beregarded as a thermal insulator. A variety of materials in variouscombinations and forms have been used for this pur- Commercial heatinsulators may be classified as of four types, namely: loose-fillinsulation, flexible blanket type, rigid board type and semi-rigid boardtype. The ideal heat insulator, however, has been found to be anadequate space of still air. Still air offers less heat conductance thanany practical medium known.

That heat insulator which shall most nearly .approach the ideal must beone in which still air is maintained with the least amount of materialpossible for practical use.

Heat insulation for buildings must comply with fire underwritersrestrictions in that it shall not be of a conflagratory nature.

. It is also desirable that such insulation may be obtained in a formthat maybe readily and easily applied over any surface.

Considering the characteristics of the heat insulators on the market,one may observethat much improvement may yet be made.

The distinctive features which I have developed in my heat insulator arethese: it shows, according ,to experts tests, a higher heat insulatingvalue, weight and volume considered, than any insulator other than stillair, and that, although it is made wholly of paper, a highly combustiblecellulosic material, it nevertheless resists combustion and cannot bemade to confiagrate or burn of itself. It is fire proof.

A blow torch will slowly burn a hole in this insulating board, butcannot kindle it to self confiagration, for when the torch is removedthe fire dies out quickly. -'I'his property is due partly to theconstruction of the board and to the fireproofing cement used to bindits members together into a permanent structure.

The semi-rigid quality of this insulating board renders it particularlyapplicable to heat insulation of buildings. The board may be scoredlengthwise or crosswise and bent to acute angles without breaking apart,and it does not appreciably warp or shrink.

The merits of my fire proof heat insulator, I ve attained through acombination of materials and structure embodying certain principleswhich I shall further set forth in the following specification, drawingand claims.

To produce an effective heat insulator, as de'- fined in the earlierpart of thisapplication, I provide substantially parallel walls between6 which air is constrainedfrom circulating by cellular structurecomposed of as small a, volume of inflammable cellulosic matter as ispracticaland the whole held'together in a permanent'structure with afire-proofing cement.

Explicitly, the structure of my heat insulating board is as follows: aplurality of flat and fluted sheets of thin close-textured paper arealternately superimposed .one upon another between flat side sheets andsecured along all contacting l faces with a fireproofing cement. As willhereinafter appear, such a structure comprises, approximately a minimumquantity of solid material of low thermal conductivity (paper) and,-

approximately, a maximum quantity of a ma- 0 terial of the highestpractical thermal insulation capacity (still air) the combinationproviding greatest possible efiiciency in thermal insulation. This samestructure facilitates thorough permeation of the board with carbondioxide (CO2) throughout an appreciable area concentric with any pointof enforced combustion, and automatic retaining of such gas over andenveloping the burned area, rendering the insulator self entinguishingand fire proof.

In order to illustrate the construction herein described, referenceshould be had to the accompanying drawing forming part of the presentapplication. Throughout the several figures of the drawing likereference characters designate the same parts in the different views.

In the drawing:

Fig. 1 is a fragmentary perspective view of the invention;

Fig. 2 is a like view of a single ply;

Fig. 3 is a cross section on line 3--3 of Fig. 1, looking in thedirection of the arrows;

Fig. 4 is a fragmentary perspective view of a single ply with sheetpartly separated; and,

Fig. 5 is a front or edge viewof Fig. 4.

In the specimen taken for illustration, a five ply construction isshown, each ply comprising, a fluted sheet I and a plain sheet 2, thetwo being secured together by fireproof cement applied along the ridgesof the flutes. Five such plies with 60 an additional outside plain sheetto completely utilize the last set of flutes, makes afive-ply board suchas shown in Fig. 1. It will be understood that the cement is applied onall ridgesthose on both sides of the fluted sheets. In this 2 way, eachplain sheet, lying between two fluted sheets, as it does, is securelycemented to every ridge contacting its respective faces. In theassembly, the cement covered ridge-contacts with the plain sheets, arecontinuous from end to end. The result is a great plurality ofcontinuous parallel small-diameter tubes completely sealed againstcirculation from one to another. Only a very narrow strip of each ridgeis cement coated-just enough to correspond to that contacted by theadiacent plain sheet. When first applied, it may be considered as anarrow thin cap, such as indicated, considerably exaggerated, at 3 inFig. 5. As the plain sheet contacts the ridge; the cap will be spreadlaterally, very slightly, having minimum thickness or depth at the lineof contact and increasing outwardly from each side of the contact, asindicated. This makes a complete seal throughout the length of everyflute. Due, partly, to the fibrous nature of the material, lateralspread of the cement, as the sheets are brought together, is notentirely uniform. The outer boundaries of spread are somewhat irregular,as indicated at 4 in Fig. 4. It will be understood that the cementpenetrates considerably andis-appreciably absorbed by the sheets itconnects, very slightly increasing their thickness along such lines ofcontact, the total increase for a five ply board of the kind illustratedbeing about .022 of an inch, along the lines of contact. This provides apermanent structure of tubes in which all tubes are independent and inwhich every tube is completely isolated from every other tube and,furthermore, one in which there is no possible looseness or chance ofair circulation between the sheets, at any point or at any time.

On reference to Figs. 4 and. 5, it will be seen that the total areacovered by cement is a small fraction, only, of the total sheet area.All but that small fraction is entirely unprotected by cement and is ofa readily inflammable nature. Ce-

ment is not indicated in Figs. 1 and 2 as suchindication would lead onlyto confusion because of the size of the views.'

The low combustibility ofthe board is due partly to the multiplicityoffine parallel, evenly distributed, thread-like strips of fireproofingcement used and to the fact that the small diameter long conduits formedby the flutes serve during enforced combustion of the board to receiveand retain carbon dioxide gas in ample quantities to extinguishexisting, and block further combustion of the board as soon as theapplied flame is withdrawn. The high temperature of the blow torch will,obviously, greatly expand the gases of combustion (mostly carbon dioxideand water vapor) at the point of combustion. This high expansion forcesthe gases into and to an appreciable distance within the tuhes,overcoming the friction of the walls. So, for an appreciable distanceradially from the burned spot, the tubes will be packed with carbondioxide, forming a thick, heavy, fire quenching blanket completelyenveloping and overlying the burned area. This will remain even for aconsiderable time after the blow torch has been removed. The wallfriction, checking the inward flow of the gas, maintains the tubesfilled continuously back to and including their smoldering ends. Thisassures the effective, operative, smothering or enveloping position ofthe gas blanket until it slowly dissipates, which is more than amplylong enough to effect thorough and complete fire extinguishing.

Only within small limits can increases in the size of the flutes be madewithout impairing the character of the board as a heat insulator and asa fire resistor. Increasing the size of the fines decreases wallfriction or resistance to air circulation and diminishes ability to holdand retain carbon dioxide gas in a sufficient quantity, 5 7

also the quantity of flreprooflng cement would be proportionatelyinsufficient to be effective. Evidently there is a means that must bemet between an excess of cellulosic matter and an excess of total freeair within the tubes or cells in a given 10 area and thickness of theboard.

In the manufacture of corrugated paper and boxes made therefrom,silicate of soda is the most generally used cement. Silicate of soda orits equivalent, as an adhesive, is more effective than 15 cements whichwould be softened by water vapor. Because it is not affected by watervapor, it continues, as a skeleton-work, to hold the carbonized orcharred p'aper intact to form a fireproof shield between any flame andthe unburned 10 paper underneath; But, other cements which would besoftened by the water vapor would fail, the charred parts would fallaway. and the unburned paper beneath would be exposed to the flame andburn. It would not be fireproof. Q6

In the construction of my insulation I prefer to use a 25 lb.machine-glazed kraft paper of about .003 inch thickness. The flutedsheets have fifty-two flutes to the foot and are 3/32" thick measuredfrom peak to valley, or, in the direc- 10 tion of the thickness of thefireproof insulator. In a five ply board of this insulation onehalf inchthick the solid cellulosic stock thickness is approximately .040",leaving a still air space .460".

In this preferred structure the total paper or {Q cellulosic solids willbe found to be approximately, 7.70% of the entire volume. While this iscited as a preferred construction, I have obtained highly satisfactoryresults from a considerable range of other dimensions and proportions ofpaper, in- Q eluding 8, 9 and 10 plies per inch, of sheets of kraftpaper ranging in thickness from .0025" to .004"- and having from 36 to52 corrugations to the foot. With fewer than 8 plies to the inch ofthickness and 42 corrugations to the lineal foot. iii from paper 16"wide, so that the flutes will be 16" long, the structure is notdependably flre proof when a blow torch is applied midway of the lengthof the corrugations. The increase in cross section of the tube, inproportion to the length, 50, appears to so reduce wall friction, thatthe carbon dioxide generated, expanded by the heat of the blow torch,apparently, flows too far into the tubes to act as an extinguisher atthe charred ends. But, if the length of this same tube or Ecorrugationis increased suiliciently, as by making it from sheets 30"wide, for instance, the insulator becomes fire proof. Thus, 8 ply sheetsof .003" and .004" paper with 36 corrugations V to the foot are fireproof when made from paper (I 30" wide, giving flutes about 13" longfrom a burned center. Applying the same tests toan insulator of thepreferred construction, specimens 16", 12" and 9" square were used. Ablow torch burned a hole through the center of each,

leaving tubes substantially 6", 4" and 3" long, from the charred edges.It is not practical to apply a hot flame such as that of a blow torch toa sheet less than 9" x 9", as the spread of flame would practicallyenvelope the whole sur 701 face of such a smaller'sheet. They were allthoroughly fire proof. S0, available data indicates that minimum lengthof tube is determined by the ratio between the peak-to-valley diameterand the length. That ratio must be such that 15:,

the wall friction of the tube will so retard the flow of carbon dioxide,when heated, as to hold it within the near ends of the tubes. Increasein length of tubes, apparently, permits increase in peak-to-valleydiameter. While there may be the present a minimum length for a givendiameter of tube, there is, seemingly, no maximum, other than thatimposed by manufacturing facilities.

As previously stated, there is, evidently, a mean that must be metbetween an excess of matter and an excess of free air. Or, there is anapproximate allowable proportion of total cellulosic solids relativelyto total air. I have found that ten plies to the inch with 52corrugations to the foot, eight plies to the inch with 42 corrugationsto the foot, and eight plies to the inch with thirtysix (36)corrugations to the foot, all gave fire proof insulators when made frommachine glazed kraft paper .0025", .003" or .004" sheets. The volumepercentage of cellulosic solids in the above will be found to be,approximately, 10% in the densest, not appreciably over. When the volumeof cellulosic solids is appreciably in ex cess of 10%, due to the use ofmore than 52 corrugations to the foot, or more than ten plies to theinch, or paper more than .004" in thickness, the insulator is no longerdependably fireproof. There then seems to be too great a percentage ofcellulosic solids. So, in constructing this fireproof insulator frompaper, the total paper incorporated, apparently, should not appreciablyexceed 10% of .the total volume. Sheets thinner than .0025" areimpractical of manufacture at time for this construction but arethoroughly acceptable, otherwise and may be used when suitablefacilities have been developed.

Kraft paper has been mentioned as the preferred type because it iseasily obtained at a moderate price in practically any locality, may bereadily had in any desired widths (for tube lengths) and thicknesses,and because it has the desired closeness of texture and is well adaptedto the corrugating process. Any other applicable papers may, obviously,be used.

The fireproof characteristics of this paper thermal insulator (100%highly inflammable cellulose) and air, are the result of lst. Soproportioning the flutes or tubes that, under enforced combustion theywill frictionally hold a smothering or fire quenching blanket of carbondioxide over and about the burned area.

2nd. A multiplicity of fine thread-like parallel and closely spacedstrips of fireproof cement which, as the insulator is burned, becausethe cement is not softened by water vapor, maintains its skeleton orlattice-work and holds the carbonized paper in place as a fire shieldbetween any flame and the unburned paper.

3rd. So proportioning the total still air and its distributionrelatively to the total cellulosic content and its distribution, as toprovide less that the minimum cellulosic material necessary to supportcombustion, in such an assembly.

For insulation against heat where fire hazard is not a question the sizeof flutes may be increased even to double the size, with ends closed;higher insulation values are obtained than with any other heat insulatorknown, weight and volume considered.

Maintaining the same quality of kraft paper as used in the half inchboard and increasing the size of flutes, a five ply board one inch thickmay be made having the same weight or less. The total still air space insuch a board will be .960" as the total stock thickness is still only.040".

. 3 While a five ply boardfhas been illustrated and described, it willbe understood that other numbers of plies may be used. Likewise, flutesof other shapes may be used, as, triangular,

rectangular, elliptical, etc. The paper mentioned 5 is 25 lb.machine-glazed kraft of about .003" thickness. Such designation isillustrative of a preferred paper but a number of other papers arethoroughly practicable though varying somewhat in the characteristicsgiven. While appliw cant has, to a certain extent, as a means of 11-lustration, specified certain materials and constructions, it is to beclearly understood that he is not in any degree limited to suchillustrative disclosures. Many changes may bemade, within the scope ofthe appended claims, in the materials and constructions hereindisclosed, without in any degree departing from the field of theinvention, and it is meant to include all such within this application,wherein only a single preferred form has been illustrated.

Having thus described my invention, what I claim and desire to protectby Letters Patent is:

1. A fireproof thermal insulator consisting oi a plurality of papertubes parallelly bound to- 35 gether in a permanent structure bythread-like narrow strips of fireproof cement along their lines ofcontact and completely sealing each from communication with the others,the .volume of cellulosic solids bearing such a, relation to the total30 volume of air and cellulosic solids as to render the insulatorincapable of sustaining combustion.

2. A fireproof thermal insulator consisting of a plurality of papertubes parallelly bound together in a permanent structm'e by thread-likeas narrow strips of fireproof cement along their lines of contact andcompletely sea-ling each from communication with the others, the crosssectional dimensions of said tubes bearing such relation to theirlengths that said tubes, under enforced combustion, retain carbondioxide s'ufliciently to ofi'ect extinguishment.

3 A fire proof thermal insulator comprising a plurality of alternatelydisposed plane and corrugated sheets of paper of a thickness of the or-45 den of approximately .0025" to approximately .004", fire proof cementsecuring said sheets permanently together and disposed in skeleton iormcomprising a plurality of spaced parallel threadfoot.

55 4. A fire proof thermal insulator comprising a plurality ofalternately disposed planed and corrugated sheets of paper of athickness of the order of approximately .0025". to approximately .004",said insulator having the plane sheetsoo spaced from .1" to .125" apart,approximately, both inclusive, fire proof cement securing said sheetspermanently together and disposed in skeleton form comprising aplurality of spaced parallel thread-like strips between and connectingthe sheets, the total cellulosic solids of said insulator notappreciably exceeding 10% by volume of the entire insulator. I

5. A fire proof thermal insulator comprising a a plurality ofalternately disposed plane and 'cor- 1o rugated sheets of paper of athickness of the order of approximately .0025" to approximately .004",said insulator comprising a plurality of plies .of said sheets, fireproof cementsecuring said sheets permanently together, each corru-uplurality contact between the sheets and corrugations, each corrugatedsheet having, approximately, from 36 to52, both inclusive, corrugationsper foot, the total cellulosic solids of said insulator not .appreciablyexceeding 10% by volume of the entire insulator. ,7

7. A fire proof-thermal insulator comprising a plurality of alternatelydisposed plane and corrug'ated sheets of paper of a thickness of theorder of approximately .003", said insulator having the plane sheetsspaced apart .1", approximately and each corrugated sheet havingapproximately 52 corrugations per foot, and fire proof cementpermanently connecting said sheets along the lines of contact betweensaid corruga- -tio ns'and said sheets.

8. A fire proof thermal insulator comprising alternately disposed planeand corrugated sheets ofpaper permanently secured in the formation of aplurality of parallel adjoining small diameter air containing tubes, amultiplicity of threadlike, closely spaced parallel strips of fire proofcement connecting said tubes and providing a skeleton work retainingframe, the cellulosic solids of said paper being uniformly distributedthrough said insulator and being between 5% approximately andapproximately of the total volnme of said insulator.

9. A fire proof thermal insulator comprising a plurality of alternatelydisposed plane and cormately of the total volume of rugated sheets'ofpaper of a thickness from approximately .0025" to approximately .004".said insulator having the plane sheets spaced from .1"'to .125" apart,approximately, both inclusive,

- each corrugated sheet having approximately from 5 36 to 52, bothinclusive, corrugations per foot, the total cellulosic solids of saidinsulator ranging between 5% approximately and 10% approxisaidinsulator, and fire proof cement permanently securing said 10 sheetstogether along the lines of contact between said sheets and saidcorrugations.

10. A fire proof thermal insulator comprising a body of cellulosicmaterial having a plurality of closely arranged permanent separate aircontain- 5 ing tubes extending therethrough, the volume of cellulosicsolids bearing such a relation to the total volume of air and cellulosicsolids as to ren-' der the insulator incapable of sustaining combustion,

11. A fire proof thermal insulator comprising a body of cellulosicmaterial having a plurality of closely arranged separate permanent aircontaining tubes extending therethrough, the cross sectional dimensionsof said tubes bearing such a relation to their lengths that theinsulator, under enforced combustion, will retain within said tubescarbon dioxide suificiently to effectively extinguish combustion.

12. A fire proof thermal insulator comprising a body of cellulosicmaterial having a plurality of closely arranged separate permanent aircontaining tubes extending therethrough, the volume of cllulosic solidsbearing such relation to the total-volume of cellulosic solids and airas to render the insulator incapable of sustaining combustion, and thecross sectional dimensions of the said tubes bearing such relation totheir lengths that said tubes, under enforced combustion, re-

tain carbon dioxide sufliciently to effect extinguishment.

, LAWRENCE D. MORTON.

